The present invention relates to fixtures for holding a workpiece securely to a working table, and more particularly to a fixture for holding and aligning an engine block to a working table during rebuilding.
Engine rebuilding has become a popular alternative to purchasing new engines in such fields as automobiles and watercraft. In some high performance industries, such as professional racing, teams build and rebuild their engines before every racing event. To the average consumer and the racing professional alike, accurate machining and rebuilding is a necessity for good performance and reliability in an engine.
Certain engine blocks, such as V-blocks, include a number of cylindrical bores on each side of the block that extend into a block at a common angle inclined from the vertical axis. For a given block, the central axes of the bores of one side will intersect with the central axes of the bores of the other side to form an angle, referred to herein as the xe2x80x9cV angle.xe2x80x9d The V angle will represent twice the value of the inclination of each bank of cylinders from the vertical axis.
One common type of machine used for rebuilding an engine is a reboring machine. Reboring the cylinders of an engine block employs a boring tool that is rotatably mounted on a vertically disposed shaft. The boring tool is lowered along a vertical pathway into a cylinder to rebore the cylinder. It is thus necessary for proper reboring that the cylinder be properly aligned under the boring tool and oriented such that its central axis is vertical.
Boring machines designed for use with engine blocks having a plurality of cylinders aligned in a row, referred to hereinafter as a xe2x80x9cbankxe2x80x9d of cylinders, commonly mount the engine block on a movable-working table. Such an arrangement enables the block to be moved such that each cylinder bore in a bank can be rebored while the block is fixtured in a single position on the working table. Translation of the working table is normally restricted to a straight-line pathway so that if the first cylinder in a bank is properly aligned with the machine and fixtured in place, the remaining cylinders will also be properly aligned.
In order to properly align a V-block so that an entire bank of cylinders can be rebored from a single fixtured position, it is necessary to incline the block so that the cylindrical bores are in a vertical position. The block must then be vertically and horizontally aligned or xe2x80x9cindexedxe2x80x9d with respect to the working table so that the boring tool can be lowered into each cylinder with its central axis positioned substantially in the same position as the central axis of the cylinder.
One known method of aligning and fixturing a V-block is to mount the block on a mounting fixture. A conventional mounting fixture comprises of two spaced-apart support members positioned on a working table to hold an engine block therebetween. Each support member includes two downwardly sloping walls that extend from the top of the support member to a conversion or intersection point located on the axis of symmetry to form V-shaped support members. The support members are spaced apart a necessary distance to receive an engine block therebetween. The downwardly sloping walls are each inclined from the vertical axis of the mounting fixture at an angle that is equal to half the V-angle of the block.
The mounting fixture also includes an alignment bar that is adjustably positioned parallel to and spaced apart from the working table to align the engine block between the mounting surface and the alignment bar. The alignment bar is inserted through the main bearing bore of the engine block and supported at the intersection point of each support member to properly align the engine block in the longitudinal direction of the working table. The mounting fixture further includes a second alignment bar that is routed through the camshaft bore of the engine block. The engine block is then rotated until the second alignment bar comes into contact with a block mounted to one of the downwardly sloping walls. Once the engine block is placed on the working table, and properly aligned using the first and second alignment bars, the engine block is secured in place by conventional clamps that extend from the working table to the top of the vertically disposed cylinder bank.
Although existing mounting fixtures provide a means for fixturing V-blocks, several disadvantages remain with existing models. One disadvantage in the prior art is that since neither of the alignment bars are secured to the mounting fixture, a lack of clamping force is provided against the engine block to inhibit movement and vibration of the engine block. For example, small movements and vibration in the engine block can occur due to the rotational cutting force transmitted by the reboring machine. Even small movement and vibration can cause variations in the machining since the dimensional changes in normal machining such as honing and reboring is approximately 0.001xe2x80x3. Vibration reduces the precision with which the boring tool can be positioned within the cylinder bore during the reboring process. As boring tool positioning precision drops, errors in cylinder bore dimensions and inner bore surface problems, such as pitting, increase. As a result, cylinder walls become asymmetrical during the reboring process. Asymmetrical cylinder walls are, of course, unacceptable in environments where high quality rebuilding is required or desired. Another disadvantage of the conventional mounting fixtures is that the conventional mounting fixture only permits a few surfaces (e.g. cylinder bores and cylinder bank faces) to be machined, while not accounting for different engine blocks, such as inline engine blocks and overhead cam engine blocks.
Therefore, there is a need for a fixturing system that inhibits small movement and vibration during the rebuilding process, while further providing a more flexible fixturing system that can be used with V-blocks, inline cylinder engine blocks, and overhead cam engine blocks.
A fixturing system is provided for holding an engine block during the rebuilding process. The fixturing system rigidly clamps the engine block to inhibit movement and vibration while precisely orienting the engine block for accurate machining of selected engine surfaces. The fixturing system is designed to be mounted on a working table, such as a precision T-slotted tool table, beneath a selected refinishing machine.
In accordance with an aspect of the present invention, a fixturing system is provided for affixing an engine block having rebuildable surfaces to a working table. The fixturing system includes a first clamping member adapted to be fixedly mounted to a working table. The first clamping member has a clamping surface substantially orthogonal to the top surface of the working table for clamping a first surface of an engine block. A second clamping member adapted to be fixedly mounted to a working table a remote distance from the first clamping member is also provided. The second clamping member has a clamping surface substantially orthogonal to the top surface of the working table for clamping a second surface of the engine block. The fixturing system further includes a support member operable to align the engine block parallel to the longitudinal axis of the working table. The support member is fixedly connected to the first and second clamping members to eliminate relative movement between the fixturing system and the engine block when the engine block is clamped therebetween.
In one embodiment of the present invention, the fixturing system further includes an indexing member operably associated with the first and second clamping member for indexing the engine block between the first and second clamping members such that a pre-selected rebuildable surface of the engine is properly aligned with a rebuilding machine associated with the working table.
In accordance with another aspect of the present invention, a fixturing system is provided for affixing an engine block having rebuildable surfaces to a working table. The fixturing system includes a first clamping member adapted to be slideably mounted to a working table along a longitudinal path of travel of the working table. The first clamping member is selectively positionable in an unsecured position, wherein the first clamping member is operable to translate along the longitudinal path of travel, and selectively positionable in a secured position, wherein the first clamping member is fixedly secured at a desired position along the longitudinal path of travel. The first clamping member has a first clamping surface substantially orthogonal to the top surface of the working table. A second clamping member adapted to be slideably mounted to a working table along a longitudinal path of travel of the working table a remote distance from the first clamping member is also provided. The second clamping member is selectively positionable in an unsecured position, wherein the second clamping member is operable to translate along the longitudinal path of travel, and selectively positionable in a secured position, wherein the second clamping member is fixedly secured at a desired position along the longitudinal path of travel. The second clamping member has a second clamping surface substantially orthogonal to the top surface of the working table. The fixturing system further includes a support member operable to align the engine block parallel to the longitudinal axis of the working table. The support member is fixedly connected to the first and second clamping members to eliminate relative movement between the fixturing system and the engine block when the engine block is clamped therebetween.
In accordance with yet another aspect of the present invention, a fixturing system is provided for affixing an engine block having rebuildable surfaces to a working table. The fixturing system includes a first clamping member adapted to be fixedly mounted to a working table. The first clamping member has a first surface substantially orthogonal to the top surface of the working table. A second clamping member is provided, which is adapted to be fixedly mounted to a working table a remote distance from the first clamping member. The fixturing system also includes a truing member having spaced-apart notches. The alignment member is secured to the first surface of the first clamping member such that the notches are orthogonal to the top surface of the working table. An alignment bar adapted to be engaged by the main bearing grooves of the engine block is further provided. The alignment bar is operable to engage the alignment notches such that the alignment bar is orthogonal to the top surface of the working table. The fixturing system further includes an elongate rod selectively secured to the second clamping member. One end of the elongate rod is adapted to engage against the engine block to clamp the engine block between the first clamping member and the end of the elongate rod.
In accordance with still another aspect of the present invention, a method of fixturing an engine block having rebuildable surfaces to a working table is provided. The working table is operably coupled to a rebuilding machine. The method includes securing a first clamping member to the working table. The first clamping member has a first clamping surface. A second clamping member having a second clamping surface is positioned on the working table a spaced-apart distance from the first clamping member. The spaced apart-distance is capable of receiving an engine block therebetween. An engine block is then positioned between the first and second clamping surfaces of the first and second clamping member. The engine block is aligned between the first and second clamping members with a support member and the ends of the support member are fixedly secured to the first and second clamping members. The engine block is then clamped between the first and second clamping surfaces.
In one embodiment, before the engine block is clamped, the engine block is indexed with an indexing member so that a pre-selected engine surface is vertically aligned with the rebuilding machine.
In accordance with still yet another aspect of the present invention, a method of fixturing an engine block having rebuildable surfaces to a working table is provided. The working table is operably coupled to a rebuilding machine. The method includes securing a first clamping member to the working table. The first clamping member has a first surface. A truing member is secured to the first surface of the first clamping member in a removable fashion. The truing member has vertically aligned spaced-apart notches. A second clamping member is positioned to the working table a spaced-apart distance from the first clamping member. The spaced apart-distance is capable of receiving an engine block therebetween. An engine block is positioned between the first and second clamping members such that the longitudinal axis of the engine block is orthogonal to the top surface of the working table. The engine block is aligned between the first and second clamping members with an alignment bar. The alignment bar is positioned between the spaced-apart notches of the truing member and the main bearing grooves of the engine block. The engine block is then clamped between the first and second clamping members.